The president of the Czech Republic, Vaclav Klaus, has signed the EU's Lisbon Treaty, the final step in the charter's ratification.

Klaus' decision to ratify the Treaty came after the Czech Republic's constitutional court rejected a last minute legal challenge from a group of eurosceptic senators and ruled that the Lisbon Treaty does not violate the country's constitution. This was seen as the removal of the final obstacle standing in the way of Klaus's signature.

Klaus’s recalcitrance made the Czech Republic the last of the EU’s 27 member states to ratify the treaty, which will give the bloc a full-time president and a more powerful foreign policy chief which advocates insist will boost its standing on the world stage. Critics, on the other hand, say it will cede too many national powers to Brussels.

The treaty could now come into force as early as December.

Speaking in Washington ahead of an EU-US summit, the European Commission's Portuguese president Jose Manuel Barroso welcomed the removal of the "last hurdle" to the treaty's passage.

"I think that the transformational potential that is there, the new external profile for the European Union, will be felt immediately," he said.